Currently, pressure sensors used in electronic blood pressure meters include a semiconductor silicon type pressure sensor and a variable electrostatic capacity type pressure sensor.
A typical electrostatic capacity type pressure sensor was disclosed in a Japanese patent entitled Manufacture of Capacitive Pressure Sensor, with the publication number of JP6307959. As shown in FIG. 1, the conventional electrostatic capacity type pressure sensor comprises a base 10, an air nozzle 11 and a diaphragm plate 12 (elastic member) which are fixed on the base 10, a fixed electrode plate 15 fixed on the base 10, and a movable electrode plate 14 arranged to be parallel to the fixed electrode plate 15. The movable electrode plate 14 and the diaphragm plate 12 (elastic member) are of an up-down structure, and the movable electrode plate 14 is assembled on the diaphragm plate 12, such as by soldering.
The present inventor filed a Chinese patent entitled Electrostatic Capacity Type Pressure Sensor and Blood Pressure Meter using the same, with the publication number of CN1932460. As shown in FIGS. 2 and 3, a pressure sensor disclosed in the Chinese patent application comprises a base assembly 21, a diaphragm plate 22, a movable electrode 23 and a fixed electrode (not shown), wherein the base assembly 21 is an integrated hardware part including an air nozzle 21c, a base 21b and a movable electrode terminal 21a, and the movable electrode 23 is assembled on the diaphragm plate 22, such as by soldering.
Similarly, a typical electrostatic capacity type pressure sensor is disclosed in a US patent entitled CENTER-MOUNT CAPACITIVE SENSOR WITH OVERLOAD PROTECTION, with the patent number of U.S. Pat. No. 6,718,827B1. In this patent, capacitor plate 60 and elastic member 20 are of an up-down structure connected by fixed post 50.
In the prior art, on one hand, the capacitor plate and elastic member need to be manufactured separately, and on the other hand, when the sensor needs to be microminiaturized, there may have difficulty in connecting the capacitor plate with the elastic member of such microminiaturized up-down structure. For example, the difficulty in assembling the thin diaphragm plate with the small movable electrode will prevent the improvement of the production efficiency of the sensor. Moreover, the assembly error between the diaphragm plate and the movable electrode may also cause parallel errors and distance errors between the fixed electrode and the movable electrode of the sensor, which may affect the linearity, thus impacting the accuracy of the sensor.